Inflatable evacuation slides typically are provided as means for emergency egress from aircraft or other people-containing structures. Controlling deployment of these slides so as to allow them to function correctly in emergency situations is thus of especial importance. Deployment control may be difficult in certain circumstances, however; as an example, if extended fully while only slightly inflated, a slide may be vulnerable to wind deflection repositioning its distal end such that the slide is unsuitable for passenger transit even when more completely inflated. Conversely, controls that prevent adequate inflation of a slide likewise would be problematic.
Conventionally, assemblies of cords and wires, referred to as frangible links, have been used for deployment control. Such a link is placed between proximal and distal ends of a folded, uninflated slide. As the slide inflates, it attempts to unfold but is restrained by the link. Further inflation eventually tensions the wire past its breaking point, at which time the slide may fully unfold for use.
U.S. Pat. No. 4,460,062 to Fisher describes another restraint system for evacuation slides designed especially for installation in the upper deck of a Boeing 747 aircraft. It replaces the frangible links described above with shear pins. The Fisher '062 patent also details a secondary restraint in the form of a cord laced in a lanyard knot, which cord unlaces upon contact with an inflatable bag. U.S. Pat. No. 4,567,977 to Fisher discloses an alternate secondary restraint including a piston and coil spring.
U.S. Pat. No. 5,711,495 to Danielson illustrates yet another restraint system for inflatable evacuation slides. This system of the Danielson patent provides friction braking means incorporating spooled webbing. As stated in the patent: “Unrolling of the webbing from the spool permits the controlled extension of the inflated tubes until the full extension of the length of webbing occurs, at which time the webbing pulls free from the spool resulting in the full release of the particular fold being restrained.” See Danielson, col. 4, 11. 26-30 (numerals omitted).